Sesquicyanines



Patented Aug. 22, 1950 SESQUI'CYANINES Douglas William Stammers,Blackley, Manchester, England, assignor to Imperial Chemical IndustriesLimited, a corporation Britain of Great No Drawing. Application July 18,1945, Serial No. 605,833. In Great Britain August 21, 194.4

6 Claims. 1

The present invention relates to the manufacture of new sesquicyanines,more particularly sesquicyanines which are characterised by containingat least one 1:5-phenanthroline nucleus. The new compounds are useful asphotographic sensitisers and this application is a further feature ofthe invention.

Sesquicyanines can be regarded as compounds exhibiting a structurecomposed of three heterocyclic nitrogen nuclei, one of which is in theform of a quaternary salt, each being joined to a central carbon atom bya methine link attached in the position a or Y- to the nitrogen atom. Ihave now found that new sesquicyanines characterised in that at leastone of the three nuclei is a 1:5-phenanthroline nucleus linked in the2-position, are eminently fitted to serve as photo-- graphicsensitisers.

According to the invention new sesquicyanines are manufactured by aprocess comprising condensing a trimethine cyanine compound, carrying inthe meso or {S-methine group an alkyl substituent, with a quaternarysalt of a heterocyclic nitrogen compound bearing in the aor 'y-positionto the nitrogen atom a substituent being alkylmercapto, aralkylmercapto,arylmercapto, or halogeno, the before mentioned trimethine cyaninecompound and heterocyclic nitrogen compound being such that theresultant sesquicyanine contains at least one 1:5-phenanthroline nucleuswhich is joined in the 2-position by a methine link to the centralcarbon atom.

It will be apparent from what has been said above that the present newsesquicyanines may contain one, two or three 1:5-phenanthroline nuclei.Thus the trimethine cyanine compound may be symmetrical orunsymmetrical. For instance, (3-ethylbenzthiazo1e-2)(3-ethylbenzoxazole-Z)-meso-methy1trimethine cyanine iodide may becondensed with 2-methylmercapto-1z5- phenanthroline ethyl p-toluenesulphonate. The resulting sesquicyanine contains one benzthiazolenucleus, one benzoxazole nucleus and one 1:5- phenanthroline nucleus.Further, bis(N--ethylbenzthiazole-Z)-meso-methyltrimethine cyanineiodide can be condensed with 2-methy1mercapto- 1:5-phenanthroline ethylp-toluene sulnhonate. In this manner a sesquicyanine with twobenzthiazole nuclei and one 1:5-phenanthroline nucleus is produced.

The trimethine cyanine compounds containing one or two1:5-phenanthroline nuclei may be made, as described in copendingapplication Serial No. 602,169, by condensing a quaternary salt of aheterocyclic nitrogen compound bearing in the aor -position to thequaternary nitrogen atom a fl-alkylmercapto- 8-alkylviny1 grouping witha heterocyclic nitrogen compound containing a methyl group in the a or 7position to a quaternary nitrogen atom, one or both of said heterocyclicnitrogen compounds being a 1:5- phenanthroline derivative.

Other phenanthroline quaternar salts which may be condensed withmeso-alkyltrimethine cyanine compounds are, for example,

2-methylmercapto-1 E-phenanthroline methyl p-toluene sulphonate(obtainable as described in my co-pending application Serial No.602,169)

Z-iodo-l :5-phenanthroline ethiodide (obtained as described in theJournal of the Chemical Society, 1942, pages 213-218) or (provided thetrimethine cyanine compound already contains at least one1:5-phenanthro1ine nucleus) 2-methylmercaptoquinoline methioolide2-methylmercapto-2 :1-naphthathiazole ethiodide2-methylmercaptobenzthiazole ethyl p-toluene sulphonate.

Examples of suitable trimethine cyanine compounds, i. e. such as containan alkyl substituent on the central carbon atom of the trimethine chain,besides the two mentioned above, are:

(3ethylbenzselenazole-2) (3-ethylbenzthiazole- 2) -meso-methyltrimethinecyanine iodide bis-(3 B hydroxyethylbenzthiazole-Z) -mesoethyltrimethinecyanine iodide (l-ethylquinoline 2) (N-ethylbenzthiazole-Z)meso-methyltrimethine cyanine p-toluene sulphonate (N-methyl [3naphthathiazole-Z) (N-methylbenzoxazole) -meso methyltrimethine cyanineiodide bis-(3 [i hydroxyethylbenzthiazole-2)mesomethyltrimethine cyanineiodide.

Such trimethine cyanine compounds are obtainable by processes which aredescribed in British specifications Nos. 412,309, 537,961, 538,875 and553,264 (Vide line 5'7 et seq. of p. 5).

The condensations according to the present invention are convenientlyefiected in the presence of an acid-binding agent, e. g. pyridine(useful also as a medium for the reaction when employed in sufiicientquantity) or often better as being a stronger base, triethanolamine ortriethylamine. Inorganic acid-binders may also be used, e. g. sodiumcarbonate.

A further feature of this invention lies in the incorporation of the newsesquicyanines as sensitisers in photographic silver halide emulsions.

1 6 p esent new sesquicyanines may be incorporated in the photographicemulsion to be sensitised by any process known in the art. For example,solutions of the new sesquicyanines in a solvent compatible with theemulsions, e. g. methanol or acetone, ma be mixed slowly with the moltenwashed gelatino-silver halide emulsion until the sesquicyanin isuniformly distributed throughout the emulsion. Or else, for instance, aphotographic emulsion with which a support, e. g. a glass plate, or filmbase, has been coated, may be sensitised by bathing the coated supportin a solution of the sesquicyanine.

The following examples i lustrate but are not intended to limit theinvention.

Example .1

0.6 gram of(3-ethyl-benzthiazole-2)(3-ethylbenzoxazole-Z)-meso-methyltrimethinecyanine iodide and 0.696 gram of 2-methylrnercapto-1:5- phenanthrolineethyl p-toluene sulphonate (b tainable as described in our copendingapplica- -tion Serial No. 602,169) are dissolved in 6 ccs. of

pyridine containing 0.69 cc. of triethylamine. The

mixture is boiled under reflux for one hour. After cooling the crude newsesquicyanine is precipitated by the addition of ether and is purifiedby washing with water and recrystallisation from methanol. The newcompound then consists of small bright green needles melting at 218 C.after preliminary softening.

9 1 CH=C N 10 s C2415 \I CHzO/ N Jlzfit Example 2 0.95 gram of bis(N-ethylbenzthiazole-2) -mesomethyltrimethine cyanine iodide and 1.065gms. of 2-methylmercapto-1:S-phenanthroline ethyl p-toluene sulphonateare dissolved in 10 cos. of dry pyridine containing 1.0 cc. oftriethylamine. The mixture is heated at the boil under reflux for onehour. After cooling and dilution with ether the new sesquicyanineseparates as an oil which solidifies when washed with cold water. Thecrude product is recrystallised twice from methanol and then consists ofgolden yellow plate-like crystals, melting at 230 Cv after sintering at210 C.

7 N 8 4 CH=C 3 2 I 9 \N CH=C 02m 04b \I s I claim: 1. The newsesquicyanine dyes con: C-CH=C Y 1 OR N of the formula:

where R1, R2, and R3 are alkyl radicals, X is the negative radical of anacid, W, Q, and Y constitute the atoms necessary to complete aheterocyclic nucleus selected from the group consisting of1:5-phenanthroline, benzthiazole and benzoxazole, at least one of thesymbols W, Q, and Y representing the atoms necessary to complete a1:5-phenanthroline nucleus which is linked to the acyclic chain of atomsin the 2-position of said phenanthroline nucleus, and R is a membertaken from the group consisting of hydrogen and alkyl radicals.

2. The new sesquicyanine dyes of the formula:

4. A sesquicyanine dye of the formula:

6 4 CH=C/S\O a 9 z-on=o 5.115

CH=C\N/O 5. The process which comprises condensing a mesoalkylsubstituted cyanine dye of the formula:

CzH5

5 with a cyclammonium salt of the formula:

where X is the negative radical of an acid, W, Q, and Y represent theatoms to complete a heterocyclic nucleus selected from the groupconsisting of 1:5 phenanthroline, benzthiazole and benzoxazole, at leastone of which is a 1:5-phenanthroline nucleus, R is a, member taken fromthe group consisting of hydrogen and alkyl, R1, R2, R3 are alkylradicals, and A is a member taken from the group consisting ofhydrocarbon mercapto and halogen in the presence of an acid bindingagent.

DOUGLAS WILLIAM STAMMERS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,104,855 Dieterle Jan. 11, 19382,185,798 Stevens Jan. 2, 1940

